This competitive renewal for a training program in Cancer Epidemiology, Biostatistics, and Environmental Health Sciences stems from the belief that high-quality investigators in these areas relating to cancer and public health will require, aside from expertise in their own specific disciplines, a broad-based multidisciplinary perspective in order to conduct and direct effective research programs. In addition to the above areas, a more-than-superficial understanding of molecular genetics, clinical oncology, toxicology, and behavioral science will also be essential. For 20 years, this Training Program has placed its emphasis on bringing a broad-based curriculum to our trainees while they pursue their own individual specific research disciplines in depth. This renewal proposes an enhanced basic science curriculum for trainees. The Epidemiology component focuses on the acquisition of the knowledge necessary to formulate meaningful hypotheses, and to design, conduct, analyze and interpret epidemiologic studies concerned with cancer etiology and prevention. The Biostatistics component emphasizes the development and application of statistical methods in studies of survival, etiology, prevention and risk assessment. The Environmental Health Sciences component has a dual emphasis: the design and conduct of molecular epidemiologic studies, and the development and application of laboratory methods for assaying human samples. At the pre-doctoral level, our Program emphasizes the development of expertise in methodology and substantive knowledge through coursework, seminars, and research experience. At the post-doctoral level, the emphasis is on supervised research and seminars, with formal courses included when desirable. Five predoctoral and four postdoctoral positions annually are requested. Opportunities for research for all the trainees are available with 40 faculty Preceptors in the participating Departments of the Mailman School of Public Health, with a large number of funded projects available. Several new recruits to the faculty, both senior and junior, as well as new leadership and re-organization of the Herbert Irving Comprehensive Cancer Center at Columbia, have all strengthened these opportunities and choices. All trainees are expected to take certain courses, e.g., Frontiers in Scientific Conduct and a course in pathology. A seminar series is held weekly, attended by all the trainees and faculty, at which each trainee presents twice each year, facilitating interaction among the trainees and faculty, and providing an opportunity for public speaking experience. Our track record for alumni of the Program has been impressive, and applications have increased with improving qualifications of applicants, as well as increased diversity.